1. Field of the Invention
The present invention relates to a frame sequential type imaging apparatus in which frame sequential light is irradiated on an object and an object image is photoelectrically converted and picked up by a solid state imaging device.
2. Description of the Related Art
Several kinds of frame sequential type imaging apparatuses which irradiate frame sequential light on an object and which photoelectrically convert and pick up an object image have been proposed.
A solid state imaging device used in these frame sequential type imaging apparatuses is composed of a plurality of picture elements for imaging. The imaging resolution by means of a solid state imaging device is largely affected by the number of the picture elements for imaging.
Recent integration technology has brought about increases in the number of the picture elements for imaging and improvement in imaging resolution resulting in an increase in the demand for high resolution in an object image display.
In such a condition, in order to substantially improve the imaging resolution by imaging devices, it has been recently proposed that an imaging element is vibrated by 1/2 pitch of a picture element interval perpendicularly to an optical path by piezoelectrics or the like, or that an object image formed on an imaging surface of an imaging device is shifted by 1/2 pitch of a picture element interval by providing a vibrating prism on an optical path, or that an optical axis of incident light is shifted by an optical system to shift 1/2 pitch of a picture element interval of an object image on a forming image device.
However, a driving means, such as piezoelectrics, is needed to vibrate a prism placed in an imaging device or on an optical path. For example, in a case of limited space, such as a tip portion of an electronic endoscope which is one of frame sequential type imaging apparatuses, driving means cannot be attached to the tip portion, or even if attached, there has been inconvenience such that the tip shape becomes larger.
Also, there has been a problem of effect on mechanical durability of an apparatus by vibration of driving means, although the problem is not limited to an electronic endoscope.
Further, in a conventional type which optically shifts an optical axis of an incident light, incident light has a plurality of wavelength ranges and all of the optical axes of the light of the wavelength ranges are shifted, so that an object image on a forming image device is shifted. Therefore, an optical system in which all optical axes are shifted for all light in every wavelength range is needed. Thus, there is a problem in which the construction of the optical system is complicated.